Question

Match each enzyme with its primary function in catecholamine synthesis:

Phenylethanolamine N-methyltransferase
Tyrosine hydroxylase
DOPA decarboxylase
Dopamine beta-hydroxylase
What is the rate-limiting step?
a) Converts dopamine to norepinephrine; Tyrosine hydroxylase
b) Converts tyrosine to L-DOPA; DOPA decarboxylase
c) Converts norepinephrine to epinephrine; Phenylethanolamine N-methyltransferase
d) Converts L-DOPA to dopamine; Dopamine beta-hydroxylase

Answer 1

The rate-limiting step in catecholamine synthesis is the conversion of tyrosine to L-DOPA by Tyrosine hydroxylase. Each enzyme is matched to its primary function in catecholamine synthesis: Tyrosine hydroxylase converts tyrosine to L-DOPA, DOPA decarboxylase converts L-DOPA to dopamine, Dopamine β-hydroxylase converts dopamine to norepinephrine, and Phenylethanolamine N-methyltransferase converts norepinephrine to epinephrine.

Step-by-step explanation:

To match each enzyme with its primary function in catecholamine synthesis and identify the rate-limiting step:

• Tyrosine hydroxylase is the enzyme that converts tyrosine to L-DOPA, and this is the rate-limiting step.
• DOPA decarboxylase converts L-DOPA to dopamine.
• Dopamine β-hydroxylase converts dopamine to norepinephrine.
• Phenylethanolamine N-methyltransferase converts norepinephrine to epinephrine.

Therefore, the correct matches for the enzymes and their functions as asked in the question are:

1. Converts dopamine to norepinephrine; Dopamine β-hydroxylase
2. Converts tyrosine to L-DOPA; Tyrosine hydroxylase (Rate-limiting step)
3. Converts norepinephrine to epinephrine; Phenylethanolamine N-methyltransferase
4. Converts L-DOPA to dopamine; DOPA decarboxylase